The present invention relates to a titanium oxide, to a photocatalyst using the titanium oxide and to a photocatalyst coating composition using the titanium oxide.
Ultraviolet irradiation to a semiconductor generates electrons having a strong reduction activity and positive holes having a strong oxidation activity, to decompose a molecular species that comes in contact with the semiconductor by an oxidation-reduction activity. Such an activity is called a photocatalytic activity. By the photocatalytic activity, NOx in the atmosphere is decomposed, bad-smelling substances, molds or the like in a living or working space are decomposed and removed, environmental pollution substances such as organic solvents, agrochemicals and surfactants in water are decomposes and removed. As a substance showing the photocatalytic activity, titanium oxide is attracting much attention and photocatalysts made of titanium oxide are in the market.
However, the photocatalytic activity shown by the photocatalysts made of titanium oxide available in the present market is not sufficient when the photocatalysts are irradiated with visible light.
The objects of the present invention is to provide a titanium oxide that shows sufficiently high photocatalytic activities by irradiation of visible light, to provide a photocatalyst using the titanium oxide as a catalyst component and to provide a photocatalyst coating composition using the titanium oxide.
The present inventors have studied on titanium oxide in order to achieve such objects. As a result, the present inventors have found that a specific titanium oxide shows sufficiently high photocatalytic activities by irradiation of visible light, and have completed the present invention.
Thus, the present invention provides a titanium oxide having
(i) three or more peaks within the range of from 1.930 to 2.030 in g value of electron spin resonance spectrum of the titanium oxide, wherein the largest one of the peaks is within the range of from 1.990 to 2.020 in the g value and/or
(ii) a spin concentration X of 1.50xc3x971016 spins/g or more, which is determined from electron spin resonance spectrum of the titanium oxide measured after irradiation of visible light.
The present invention also provides a photocatalyst containing the above-described titanium oxide as a catalyst component.
The invention further provides a photocatalyst coating composition comprising the above-described titanium oxide and a solvent.